Motor vehicle lock-up clutch control apparatus, having means for detecting clutch judder with high accuracy

Abstract

An apparatus for controlling a lock-up clutch between pump and turbine impellers in a power transmitting system of a motor vehicle, including a slip control device for controlling the amount of slip of the lock-up clutch, and a judder detector for detecting a judder of the lock-up clutch based on the number of detected speed variations of the turbine impeller during slip control of the lock-up clutch by the slip control device, wherein the judder detector is inhibited from using a variation of the turbine impeller speed variation for the detection of the judder, if the amount of change of the variation amplitude is larger than a predetermined threshold or if the period of the variation is outside a predetermined range. The judder detector is preferably arranged to operate on the basis of the variation amplitude of the turbine impeller speed as compared with the variation amplitude of the output speed of an automatic transmission multiplied by the actual speed ratio of the transmission, or on the basis of a phase difference between the variation waveforms of the turbine impeller and transmission output speeds.

What is claimed is: 
     
       1. An apparatus for controlling an amount of slip of a lock-up clutch disposed between a pump impeller and a turbine impeller in a power transmitting system of a motor vehicle, said apparatus comprising: slip control means for controlling the amount of slip of said lock-up clutch such that an actual slip speed of said lock-up clutch coincides with a predetermined target slip speed;   speed variation monitoring means for detecting variations of a rotating speed of said turbine impeller;   judder determining means connected to said speed variation monitoring means, for determining the presence or absence of a judder of said lock-up clutch on the basis of the number of said variations detected by said speed variation monitoring means during slip control of said lock-up clutch by said slip control means, and for inhibiting operation of said slip control means if in the presence of said judder;   variation amplitude determining means connected to said speed variation monitoring means, for determining an amplitude of each of said variations of said rotating speed of said turbine impeller which have been detected by said speed variation monitoring means; and   amplitude change monitoring means connected to said variation amplitude determining means, for determining, on the basis of the amplitudes of two successive variations determined by said variation amplitude determining means, whether an amount of change of the amplitudes of said two successive variations is larger than a predetermined upper limit, and inhibiting said judder determining means from using at least a latter one of said two successive variations for the determination of the presence or absence of said judder of said lock-up clutch, if said amount of change determined is larger than said predetermined upper limit.   
     
     
       2. An apparatus according to claim 1, wherein said speed variation monitoring means detects, as each of said variations of the rotating speed of said turbine impeller, two adjacent upper and lower peaks of a waveform of said rotating speed, and said variation amplitude determining means determines, as said amplitude of said each variation, a difference between said two adjacent upper and lower peaks of said waveform of said rotating speed. 
     
     
       3. An apparatus according to claim 2, wherein said predetermined upper limit of said amount of change of the amplitudes of said two successive variations is determined such that said amount of change is larger than said predetermined upper limit where said variations of the rotating speed of said turbine impeller are caused due to passage of the motor vehicle through a relatively narrow local raised or recessed area of a generally good road surface during said slip control of said lock-up clutch by said slip control means. 
     
     
       4. An apparatus according to claim 1, wherein said judder determining means includes: first variation number monitoring means for determining whether the number of the variations of the rotating speeds of said turbine impeller which are detected by said speed variation monitoring means during the slip control of said lock-up clutch by said slip control means is smaller than a predetermined first threshold;   slip control interrupting means for interrupting said slip control of the lock-up clutch by said slip control means, if said first variation number monitoring means determines that the number of said variations detected by said speed variation monitoring means during said slip control is not smaller than said predetermined first threshold; and   second variation number monitoring means for determining whether the number of the variations of the rotating speed of said turbine impeller which are detected by said speed variation monitoring means during interruption of said slip control by said slip control interrupting means is smaller than a predetermined second threshold.   
     
     
       5. An apparatus according to claim 4, wherein said slip control interrupting means includes a provisional judder determination flag which is set when said first variation number monitoring means determines that the number of said variations detected by said speed variation monitoring means is not smaller than said predetermined first threshold, said slip control means being disabled when said provisional judder determination flag is set. 
     
     
       6. An apparatus according to claim 4, further comprising slip control resuming means for resuming said slip control of said lock-up clutch which has been interrupted by said slip control interrupting means, if said second variation number monitoring means determines that the number of said variations detected by said speed variation monitoring means during the interruption of said slip control is not smaller than said predetermined second threshold. 
     
     
       7. An apparatus according to claim 6, wherein said second variation number monitoring means includes first monitoring means for determining whether the number of the variations of the rotating speed of said turbine impeller detected in an initial portion of a time duration of said interruption of said slip control is smaller than said predetermined second threshold value, and second monitoring means for determining whether the number of the variations of the rotating speed of said turbine impeller detected in a latter portion of said time duration of said interruption of said slip control which follows said initial portion is smaller than a predetermined third threshold, said slip control resuming means resuming said slip control of the lock-up clutch if said second monitoring means determines that the number of the variations detected in said latter portion of said interruption of said slip control is smaller than said predetermined third threshold, after said first monitoring means determines that the number of the variations detected in said initial portion is not smaller than said predetermined second threshold. 
     
     
       8. An apparatus according to claim 7, wherein said predetermined second threshold is determined such that said number of the variations of the rotating speed of said turbine impeller detected by said first monitoring means of said speed variation monitoring means during said initial portion of said time duration of said interruption of said slip control of said lock-up clutch is not smaller than said predetermined second threshold where said variations during said interruption are caused due to running of the motor vehicle on a generally bumpy road surface during said interruption. 
     
     
       9. An apparatus according to claim 7, further comprising slip control terminating means for terminating said slip control of said lock-up clutch if said first monitoring means of said second variation number monitoring means determines that the number of said variations of the rotating speed of said turbine impeller detected by said speed variation monitoring means during said initial portion of said time duration of said interruption of said slip control is smaller than said predetermined second threshold. 
     
     
       10. An apparatus according to claim 1, further comprising: variation period determining means for determining a period of each of said variations of said rotating speed of said turbine impeller which have been detected by said speed variation monitoring means; and   variation period monitoring means for determining whether said period determined by said variation period determining means is outside a predetermined range, and inhibiting said judder determining means from using each of said variations whose periods are outside said predetermined range.   
     
     
       11. An apparatus for controlling an amount of slip of a lock-up clutch disposed between a pump impeller and a turbine impeller in a power transmitting system of a motor vehicle, said apparatus comprising: slip control means for controlling the amount of slip of said lock-up clutch such that an actual slip speed of said lock-up clutch coincides with a predetermined target slip speed;   speed variation monitoring means for detecting variations of a rotating speed of said turbine impeller;   judder determining means connected to said speed variation monitoring means, for determining the presence or absence of a judder of said lock-up clutch on the basis of the number of said variations detected by said speed variation monitoring means during slip control of said lock-up clutch by said slip control means, and for inhibiting operation of said slip control means in the presence of said judder;   variation period determining means connected to said speed variation monitoring means, for determining a period of each of said variations of said rotating speed of said turbine impeller which have been detected by said speed variation monitoring means; and   variation period monitoring means connected to said variation period determining means, for determining whether said period determined by said variation period determining means is outside a predetermined range, and inhibiting said judder determining means from using each of said variations whose periods are outside said predetermined range.   
     
     
       12. An apparatus according to claim 11, wherein said predetermined range of said period is determined such that periods of said variations of the rotating speed of said turbine impeller are held within said predetermined range where said variations are caused due to the presence of said judder of said lock-up clutch during the slip control thereof by said slip control means. 
     
     
       13. An apparatus according to claim 11, wherein said judder determining means includes: first variation number monitoring means for determining whether the number of the variations of the rotating speeds of said turbine impeller which are detected by said speed variation monitoring means during the slip control of said lock-up clutch by said slip control means is smaller than a predetermined first threshold;   slip control interrupting means for interrupting said slip control of the lock-up clutch by said slip control means, if said first variation number monitoring means determines that the number of said variations detected by said speed variation monitoring means during said slip control is not smaller than said predetermined first threshold; and   second variation number monitoring means for determining whether the number of the variations of the rotating speed of said turbine impeller which are detected by said speed variation monitoring means during interruption of said slip control by said slip control interrupting means is smaller than a predetermined second threshold.   
     
     
       14. An apparatus according to claim 13, wherein said slip control interrupting means includes a provisional judder determination flag which is set when said first variation number monitoring means determines that the number of said variations detected by said speed variation monitoring means is not smaller than said predetermined first threshold, said slip control means being disabled when said provisional judder determination flag is set. 
     
     
       15. An apparatus according to claim 13, further comprising slip control resuming means for resuming said slip control of said lock-up clutch which has been interrupted by said slip control interrupting means, if said second variation number monitoring means determines that the number of said variations detected by said speed variation monitoring means during the interruption of said slip control is not smaller than said predetermined second threshold. 
     
     
       16. An apparatus according to claim 15, wherein said second variation number monitoring means includes first monitoring means for determining whether the number of the variations of the rotating speed of said turbine impeller detected in an initial portion of a time duration of said interruption of said slip control is smaller than said predetermined second threshold value, and second monitoring means for determining whether the number of the variations of the rotating speed of said turbine impeller detected in a letter portion of said time duration of said interruption of said slip control which follows said initial portion is smaller than a predetermined third threshold, said slip control resuming means resuming said slip control of the lock-up clutch if said second monitoring means determines that the number of the variations detected in said latter portion of said interruption of said slip control is smaller than said predetermined third threshold, after said first monitoring means determines that the number of the variations detected in said initial portion is not smaller than said predetermined second threshold. 
     
     
       17. An apparatus according to claim 16, wherein said predetermined second threshold is determined such that said number of the variations of the rotating speed of said turbine impeller detected by said first monitoring means of said speed variation monitoring means during said initial portion of said time duration of said interruption of said slip control of said lock-up clutch is not smaller than said predetermined second threshold where said variations during said interruption are caused due to running of the motor vehicle on a generally bumpy road surface during said interruption. 
     
     
       18. An apparatus according to claim 16, further comprising slip control terminating means for terminating said slip control of said lock-up clutch if said first monitoring means of said second variation number monitoring means determines that the number of said variations of the rotating speed of said turbine impeller detected by said speed variation monitoring means during said initial portion of said time duration of said interruption of said slip control is smaller than said predetermined second threshold. 
     
     
       19. An apparatus for controlling an amount of slip of a lock-up clutch disposed between a pump impeller and a turbine impeller of a fluid-filled power transmitting device which is disposed between an engine and an automatic transmission of a motor vehicle such that an output torque of the engine is transmitted to the automatic transmission through said power transmitting device, said automatic transmission having an output shaft operatively connected to a drive wheel of the vehicle, said apparatus comprising: slip control means for controlling the amount of slip of said lock-up clutch such that an actual slip speed of the lock-up clutch coincides with a predetermined target slip speed;   turbine speed variation amplitude monitoring means for determining a variation amplitude of a rotating speed of said turbine impeller;   output speed variation amplitude monitoring means for determining a variation amplitude of a rotating speed of said output shaft of said automatic transmission;   speed ratio determining means for determining a speed ratio of said automatic transmission; and   judder determining means connected to said turbine speed variation amplitude monitoring means, said output speed variation amplitude monitoring means and said speed ratio determining means, for determining the presence or absence of a judder of said lock-up clutch on the basis of said variation amplitude of the rotating speed of said turbine impeller as compared with a product of said variation amplitude of the rotating speed of said output speed and said actual speed ratio of said automatic transmission, and for inhibiting operation of said slip control means in the presence of said judder.   
     
     
       20. An apparatus according to claim 19, wherein said judder determining means determines that said lock-up clutch is juddering, if said variation amplitude of the rotating speed of said turbine impeller is larger than said product. 
     
     
       21. An apparatus according to claim 19, wherein said judder determining means determines that said lock-up clutch is juddering, if said variation amplitude of the rotating speed of said turbine impeller is larger than a sum of said product and a predetermined constant. 
     
     
       22. An apparatus according to claim 19, wherein said judder determining means determines that said lock-up clutch is juddering, if a ratio of said variation amplitude of the rotating speed of said turbine impeller to said variation amplitude of the rotating speed of said output shaft is larger than said speed ratio. 
     
     
       23. An apparatus according to claim 19, further comprising slip control terminating means for terminating slip control of said lock-up clutch by said slip control means if said judder determining means determines that said lock-up clutch is juddering. 
     
     
       24. An apparatus according to claim 19, further comprising variation change monitoring means for determining whether an amount of change of the amplitudes of two successive variations of the rotating speed of said turbine impeller which have been determined by said turbine speed variation amplitude monitoring means is larger than a predetermined upper limit, and inhibiting said judder determining means from using at least a latter one of said two successive variations for the determination of the presence or absence of said judder of said lock-up clutch, if said amount of change determined is larger than said predetermined upper limit. 
     
     
       25. An apparatus according to claim 19, further comprising: speed variation monitoring means for detecting variations of the rotating speed of said turbine impeller;   variation period determining means for determining a period of each of variations of the rotating speed of said turbine impeller which have been detected by said speed variation monitoring means; and   variation period monitoring means for determining whether said period determined by said variation period determining means is outside a predetermined range, and inhibiting said judder determining means from using each of said variations whose periods are outside said predetermined range.   
     
     
       26. An apparatus for controlling an amount of slip of a lock-up clutch disposed between a pump impeller and a turbine impeller of a fluid-filled power transmitting device which is disposed between an engine and an automatic transmission of a motor vehicle such that an output torque of the engine is transmitted to the automatic transmission through said power transmitting device, said automatic transmission having an output shaft operatively connected to a drive wheel of the vehicle, said apparatus comprising: slip control means for controlling the amount of slip of said lock-up clutch such that an actual slip speed of the lock-up clutch coincides with a predetermined target slip speed;   a turbine speed sensor for detecting a rotating speed of said turbine impeller;   an output speed sensor for detecting a rotating speed of said output shaft of said automatic transmission;   phase difference determining means connected to said turbine speed sensor and said output speed sensor, for determining a phase difference between a variation waveform of the rotating speed of said turbine impeller and a variation waveform of the rotating speed of said output shaft; and   judder determining means connected to said phase difference determining means, for determining the presence or absence of a judder of said lock-up clutch on the basis of said phase difference determined by said phase difference determining means, as compared with a predetermined reference value, and for inhibiting operation of said slid control means in the presence of said judder.   
     
     
       27. An apparatus according to claim 26, wherein said judder determining means determines that said lock-up clutch is juddering, if a phase of said variation waveform of the rotating speed of said output shaft is advanced with respect to a phase of said variation waveform of the rotating speed of said turbine impeller by more than said predetermined reference value. 
     
     
       28. An apparatus according to claim 26, further comprising slip control terminating means for terminating slip control of said lock-up clutch by said slip control means if said judder determining means determines that said lock-up clutch is juddering. 
     
     
       29. An apparatus according to claim 26, further comprising variation change monitoring means for determining whether an amount of change of the amplitudes of two successive variations of the rotating speed of said turbine impeller which have been determined by said turbine speed variation amplitude monitoring means is larger than a predetermined upper limit, and inhibiting said judder determining means from using at least a latter one of said two successive variations for the determination of the presence or absence of said judder of said lock-up clutch, if said amount of change determined is larger than said predetermined upper limit. 
     
     
       30. An apparatus according to claim 26, further comprising: speed variation monitoring means for detecting variations of the rotating speed of said turbine impeller;   variation period determining means for determining a period of each of variations of the rotating speed of said turbine impeller which have been detected by said speed variation monitoring means; and   variation period monitoring means for determining whether said period determined by said variation period determining means is outside a predetermined range, and inhibiting said judder determining means from using each of said variations whose periods are outside said predetermined range.   
     
     
       31. An apparatus according to claim 26, further comprising: turbine speed variation amplitude monitoring means for determining a variation amplitude of the rotating speed of said turbine impeller;   output speed variation amplitude monitoring means for determining a variation amplitude of the rotating speed of said output shaft of said automatic transmission; and   speed ratio determining means for determining a speed ratio of said automatic transmission;   and wherein said judder determining means effecting a first determination as to whether said variation amplitude of the rotating speed of said turbine impeller is larger than a product of said variation amplitude of the rotating speed of said output speed and said actual speed ratio of said automatic transmission, and a second determination as to whether said phase difference is larger than said predetermined reference value, said judder determining means determining the presence of said judder of said lock-up clutch if an affirmative decision is obtained in at least one of said first and second determinations.